clang-format: Fix comment formatting bugs in nested blocks.

This fixes two issues:
1) The indent of a line comment was not adapted to the subsequent
   statement as it would be outside of a nested block.
2) A missing DryRun flag caused actualy breaks to be inserted in
   overly long comments while trying to come up with the best line
   breaking decisions.

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@190123 91177308-0d34-0410-b5e6-96231b3b80d8